Hi, It looks like threads-devel is abandoned I posted here. I have tried boost::shared_mutex and found an issue. It looks like it doesn't work as expected. The problem is following code: void lock() { #if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS boost::this_thread::disable_interruption do_not_disturb; #endif boost::unique_lockboost::mutex lk(state_change); state.exclusive_waiting_blocked=true; exclusive_cond.wait(lk, boost::bind(&state_data::can_lock, boost::ref(state))); state.exclusive=true; } On lines: state.exclusive_waiting_blocked=true; exclusive_cond.wait(lk, boost::bind(&state_data::can_lock, boost::ref(state))); Here the state is changed and new lock_shared() waits because can_lock_shared returns false in this case. It works as I think it should be. The when "old" readers unlocks mutex the last one unlock_shared() executes void unlock_shared() { ... if (state.no_shared()) { if (state.upgrade) { ... } else { state.exclusive_waiting_blocked=false; //lk.unlock(); } release_waiters(); } where resets state.exclusive_waiting_blocked value. Then notify 2 condition variables(in release_waiters): 1 for readers and 1 for writers. If the writer doesn't win this race and one of the waited readers will be the first one, the writer runs state_data::can_lock and it of course returns false. Then the writer goes to sleep again. But exclusive_waiting_blocked is still false. So in the high pressure of readers, this writer never gets a chance to get control in this case anymore until all readers are gone. This bug was introduced in 1.67 version, before the changes the code was: while (state.shared_count || state.exclusive) { state.exclusive_waiting_blocked=true; exclusive_cond.wait(lk); } but it not the same as (because exclusive_waiting_blocked reassigned): state.exclusive_waiting_blocked=true; exclusive_cond.wait(lk, boost::bind(&state_data::can_lock, boost::ref(state))) Best Regards, Maxim